Mitral valve repair has become the treatment of choice for patients with mitral regurgitation (MR) due to myxomatous leaflet degeneration and post-infarction ventricular remodeling (ischemic mitral regurgitation (IMR). In this condition, the mitral leaflets are structurally normal but valve geometry is grossly disturbed due to a variable combination of leaflet tethering and annular dilation. However, recent long-term studies have indicated that the recurrence rate of significant MR after repair is much higher than previously thought, particularly in patients with IMR. Precise three-dimensional (3D) modeling of the mitral valve has the potential to improve the understanding of valvular mechanics and to allow for an optimized patient—specific approach to mitral valve surgery. Recent technological advancement in real-time three-dimensional echocardiography (rt-3DE) overcomes the limitations of two-dimensional echocardiography by facilitating through-plane motion analysis and three-dimensional reconstruction of valve geometry. Current commercial rt-3DE software packages provide visual representations of the mitral valve but enable only simple mitral valve quantification, such as manual segmentation and user-guided measurement of the valve dimensions. It is desired to apply automated image processing methods to rt-3DE image data to provide a means of quantitatively assessing mitral valve geometry and function. Such practical, quantitative tools would have the potential to assist in clinical decision-making, to guide therapeutic intervention, to examine the outcome of prevention and treatment strategies, and to develop research models and tools for study of the function of the mitral valve.
IMR is a common clinical phenomenon that results from complex 3D changes in valve anatomy. IMR increases mortality even when mild, with a strong graded relationship between severity and reduced survival. The current surgical treatment for IMR is undersized ring annuloplasty. Results of this approach are suboptimal. Automated rt-3DE analysis has the potential to enhance the understanding of the mechanism of IMR and to improve the therapeutic result. Preclinical and clinical studies have demonstrated that IMR results from two distinct anatomic disturbances: 1) subvalvular remodeling that promotes leaflet tethering, and 2) annular dilation that produces central malcoaptation in the annular plane. Although annuloplasty effectively treats annular dilation, it does not improve and may even exacerbate leaflet tethering. Moreover, it has been demonstrated that commonly used annuloplasty devices significantly reduce leaflet curvature, thereby increasing valvular stress and further compromising repair durability. Leaflet augmentation techniques have the potential to improve repair results by alleviating leaflet tethering and flattening. However, using automated rt-3DE analysis of the mitral valve, it is believed that combining posterior leaflet augmentation with ring annuloplasty in an ovine model of IMR will decrease leaflet tethering and improve the efficacy of repair compared to undersized annuloplasty alone.
A number of imaging modalities have been utilized for qualitative and quantitative analysis of mitral valve function. These include 2D and 3D echocardiography (2DE and 3DE), magnetic resonance imaging (MRI), multidetector computed tomography (MDCT), sonomicrometry, and biplane radiation with tantalum markers. Traditionally, assessment of the mitral valve has been achieved by 2D ultrasound image analysis, which derives structural and dynamic information from one cross-sectional view of the valve. With the advent of 3D ultrasound, the possibility of obtaining a full 3D assessment of cardiac structures was introduced. This early 3D technology, however, was considerably limited by poor spatial and temporal resolution. With recent advances in transducer design and super-computed signal processing, high-resolution 3D ultrasound images of the heart can now be acquired at 20-30 frames per second. This capability, combined with the advancement of transesophageal probes, opens a previously unexplored avenue for the study of mitral valve architecture and mechanics. Although current software packages allow for manual segmentation and user-guided measurement of valve dimensions in rt-3DE datasets, the quantification is time-consuming and labor-intensive. To address this issue, it is desirable to develop a tool for comprehensive, semi-automated analysis of the mitral valve using the latest rt-3DE technology. The invention addresses these needs in the art.